This invention is concerned with the installation of door furniture particularly door handle and latch assemblies.
A door handle assembly generally comprises a pair of handles disposed one to each side of the door and coupled to a latch shaft to operate a latch which is installed in the door so that its bolt can be extended from the outer edge of the door but can be retracted by rotation of the shaft. Usually a pair of escutcheon plates are mounted against the side faces of the door to cover the hole for the latch shaft. In some cases the escutcheon plates are simply attached to the door by means of screws which remain visible but in other constructions a concealed mounting is achieved. Assemblies incorporating concealed mountings are disclosed in Australian Pat. No. 409,156 and also in our copending Australian patent application No. 16814/76 and corresponding U.S. Pat. No. 4,037,865 and Canadian application No. 258,705. In each of these cases the escutcheon plates are screw-fitted to mounting plates which are fixed to the door to carry the handles and handle shafts.
The present invention has arisen because of a demand for privacy lock sets which can be locked from one side of the door to prevent entry from the other side but can still be opened from the first side by normal operation of the handle at that side and which have much the same appearance as conventional lock sets which do not have the privacy locking function. Specifically the invention has arisen from a project to design a privacy lock set having much the same appearance as that disclosed in the above United States patent, which incorporates concealed mountings and screw-on escutcheon plates. In order to achieve this result it was necessary that the additional components needed to provide the privacy locking functions be fitted within a very confined space between the face of the door and the escutcheon plate. The invention provides a novel type of handle to shaft coupling device which enables this result to be achieved. However, from the ensuing description it will be appreciated that the invention is not limited in application to assemblies having concealed mountings and it could be applied to locksets of other types.